Both the miniaturized fuse of the invention and those disclosed in these patents preferably, but not necessarily, comprise an all fuse metal plug-in fuse element formed by stamping the same from a strip of fuse metal. The stamping forms a pair of laterally spaced juxtaposed, parallel terminal blade portions to be received by pressure clip terminals in a mounting panel, current-carrying extensions at the inner end portions of the pair of terminal blade-portions and a fuse link portion of very small cross-sectional area interconnecting the current-carrying extensions. The shape, placement and/or size and thickness of the fuse link determines the current rating of the fuse.
Generally, the method of making such a plug-in fuse assembly, and as disclosed in said U.S. patents, comprises providing a strip of fuse metal which is progressively blanked or stamped to provide longitudinally spaced, interconnected fuse-forming sections or blanks having the desired fuse element configurations as described. The spaced pairs of terminal blades are interconnected by transverse, relatively rigid webs when the fuse links are fragile. The exposed transverse webs interconnecting the pairs of terminal blades add rigidity to the strip and securely maintain the relative positions of the pairs of terminal blades, the current-carrying extensions thereof and the more fragile interconnecting fuse link, until a housing or the like is inserted over and secured to each blank. The housing is most advantageously (i.e. but not necessarily) a single piece molding preferably of transparent material having an opening at one end thereof, preferably its bottom end, which enables the housing to be readily inserted over the end most blank of the strip before it is severed from the rest of the strip, with the terminal blade portions and web positioned outside of the housing. Before the web is removed therefrom, the housing may be staked into apertures in the current-carrying extensions of the fuse metal element.
The fuse development which is the subject of the above-identified patents represents a major advance in the design of automotive fuses because the construction thereof permitted the reliable, automated, low cost production thereof, and it greatly reduced the overall size and volume of the fuses in comparison to those used previously for this purpose. With the recent increase in the number of separately fused circuits in automobiles, there has been an increased need to reduce the size of automotive fuses further, to increase the packing density thereof and decrease the space requirements of the fuse mounting blocks into which the fuses are plugged. To this end, the proposed commercial form of the present invention provides a fuse which is much shorter, narrower, thinner, and occupies much less volume than the previous fuse designs. The size reduction is facilitated by the unique shape of the all metal plug-in fuse element and its unique relationship to the housing applied thereover. Also, while some aspects of the invention do not so require, the preferred form of the invention utilizes a spacing between the confronting edges of the terminal blades which is similar to, preferably slightly greater than, that used in the larger fuses, so that the smaller fuses with narrower terminal blades can replace and be plugged into the same socket terminals as the larger fuses replaced thereby.
While the preferred form of the fuses disclosed in the aforesaid patents utilize a single piece housing with an open bottom for receiving the current-carrying extensions of the all metal fuse element, the broader aspects of the fuse design covered by the patents referred to encompass a two-piece housing used by a licensee under these patents as well as other housing configurations. The licensee's housing is a two piece housing, where the bottom part has an opening in the top thereof into which the terminal blade end of the all metal plug-in fuse element is inserted. The opening at the top of this bottom part of the housing assembly is closed by a cover piece placed and attached thereover. It was found that the former housing design having an opening at the bottom rather than at the top thereof is especially suitable for the design of a smaller fuse which is the subject of the present invention.